Seatubes makes it easy to batch download YouTube videos to your Mac. Simply drag YouTube URLs into a documents list view, then click the "Download" button. If a URL is a video URL it will be added, otherwise Seatubes will try to add all of the video URLs it contains, i.e. import the URL.
Seatubes is a multi-window (or multi-document) application. You can associate different windows with independent collections of videos, and save them to disk for future use or to share with other Seatubes users.